The present invention relates to rolling or sliding parts, and more particularly to rolling parts suitable as antifriction bearing components, such bearing rings and rolling bodies, or as sliding parts suited as sliding bearing components, for use in soiled oil containing extraneous matter.
For example for use in such antifriction bearings, the present applicant has already proposed an antifriction bearing part which comprises a steel containing 0.5 to 1.2 wt. % of C and 0.7 to 3.0 wt. % of Cr and is given a surface with a C content of 1.5 to 3.0 wt. % and a surface hardness of at least 63 in Rockwell C hardness by carburizing treatment, the bearing part having a carburized layer containing a precipitated fine spheroidal carbide in an amount of 15 to 80% in area ratio. The spheroidal carbide is up to 10 .mu.m in diameter. The matrix of the carburized layer contains 0.6 to 0.7 wt. % of C (JP-A No. 41934/1995).
However, we have found that the conventional part described still remains to be improved in life for use in antifriction bearings which are subjected to conditions of ever-increasing severity recently.